Texas Quarantines 21 Counties as Screwworm Spreads

Texas has imposed sweeping emergency quarantines across 21 counties as a New World screwworm outbreak escalates into the first US domestic case cluster in roughly 60 years. Reported on 29 June 2026, the Texas Animal Health Commission has now confirmed 26 cases of the flesh-eating parasite, with state and federal authorities accelerating a sterile insect response programme that has wider commercial implications for animal health and livestock production.

The outbreak began on 3 June 2026 with larvae detected in the umbilical wound of a three-week-old calf in Zavala County. By 8 June, further cases were confirmed in Gillespie, La Salle and Andrews counties, with the Andrews dog case traced to neighbouring New Mexico. Governor Greg Abbott formally launched the response campaign on 11 June, and TAHC Executive Director Dr Lewis R. Dinges has since signed additional emergency orders covering Jim Hogg, Starr and Zapata counties along the deep south Texas border.

The primary response tool is the Sterile Insect Technique, with USDA and international partners releasing around 500 million sterile male flies per week across affected zones and the Mexican border to drive reproductive collapse. Texas congressional leaders have flagged concerns that recent federal personnel cuts could limit response capacity, with the recommended aggressive-outbreak minimum historically at 700 million flies per week. State officials estimate the economic threat at $1.8 billion to Texas alone and $10.6 billion to national agricultural markets.

The commercial implications for animal health are substantial. A sustained outbreak would lift demand across antiparasitic treatments, wound care products and veterinary diagnostics in the affected regions, with broader pricing and supply effects across the US cattle market. The bigger question is response funding capacity, with current sterile fly volumes already below the historically recommended threshold for outbreaks of this aggression.

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